core: Remove string_length.

* module/mes/scm.mes (string-length): New function.

module/mes/scm.mes

@@ -188,6 +188,9 @@
 
 
 ;;; Strings/srfi-13
+(define (string-length s)
+  (length (string->list s)))
+
 (define (string-ref s k)
   (list-ref (string->list s) k))
 

string.c

@@ -18,13 +18,6 @@
  * along with Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-SCM
-string_length (SCM x)
-{
-  assert (TYPE (x) == STRING);
-  return MAKE_NUMBER (VALUE (length (STRING (x))));
-}
-
 SCM
 substring (SCM x) ///((arity . n))
 {